Simulation of blockage effects on scouring downstream of box culverts under unsteady flow conditions

Scouring at the downstream of culvert considered as one of the main reasons of culvert failure. Failure of the culvert structure is a catastrophic phenomenon. Studying the causes of scouring will give an idea about the solution probabilities; the blockage and geometry of culvert have a great influence on the local scour. In this study, simulated results that obtained from Flow-3D software of box culvert model and formation of scour at the outlet are compared with laboratory results of (Sorourian, 2015) to evaluate the accuracy of the numerical model. Laboratory box culvert was carried out for two conditions; the non-blocked situation and the partially blocked condition with the blockage ratio of 40%, for this destination used two different sizes of plates and the finer sediment was used in Sayana's study with the median grain size being 0.85 mm and 2.0 mm, the flow conditions in the laboratory were unsteady. It is mean that the flow rates during the time were changed. The performance of the numerical model based on renormalization group (RNG) and k-ε model compared with experimental results. The comparison shows that the RNG results has a good agreement than the k-ε model